Measuring the surface properties of roadways, and in particular runways, is becoming an important part of travel safety, and in determining when and what kind of surface maintenance is required. Aircraft pilots require up to the minute runway condition reports, including the depth of the snow and the consistency, e.g. powder or slush. Devices for measuring the depth of snow range from in-situ sensors, such as those disclosed in German Patent Publications Nos. 3204477 published May 5, 1983 in the name of Wilfried Fritzshe, and 3317298 published Jan. 3, 1985 in the name of Zillober et al, and U.S. Pat. No. 5,686,841 issued Nov. 11, 1997 to Stolarczyk to portable probes for inserting into the snow, such as those disclosed in German Patent Publication No. 19503017, published Sep. 28, 1995, and U.S. Pat. No. 5,864,059 issued Jan. 26, 1999 to Sturm et al. Japanese Patent Publication No. 2000121749 published Apr. 28, 2000 to Taminoe et al, discloses a snow depth measuring device that measures the phase difference between a light directed at the snow and that of the reflected light. All of the aforementioned systems simply measure the snow in a single spot, and therefore require multiple measurements to obtain, at best, an average value.
Vehicle mounted systems for measuring the surface roughness of roadways are disclosed in U.S. Patent Publication 2003/137673 published Jul. 24, 2003 in the name of Cox et al, and Swiss Patent No. 666349 issued Jul. 15, 1988 to Slavko Mesaric. Cox et al relies on phase profilometry, i.e. uses shadows for contrasting the surface, to generate a 3-D profile of a surface. Mesaric, on the other hand, measures the distortion of light strips marked along the surface of the road. Neither system provides a simple and easy system for measuring the characteristics of a surface, in particular snow or contaminant depth, while moving along the surface thereof.
An object of the present invention is to overcome the shortcomings of the prior art devices by providing a relatively inexpensive and simple device for measuring the surface characteristics of a roadway or runway, while driving thereon.